Re: [Alsa-devel] [PATCH] alsa: correct nonsensical sysfs device symlinks

Takashi Iwai
2007-01-26T11:40:34Z

At Fri, 26 Jan 2007 05:53:36 -0500,
xiphmont@xiph.org wrote:
>
> On 1/25/07, Greg KH <greg@kroah.com> wrote:
>
> > Is there anything else left to fix?
>
> Once that testing is done, no. But don't trust the two patches I sent
> yet, I'll resumbit the patch resulting from more thorough testing in a
> few hours (much thanks to Takashi for giving me the parent device
> feedback I was trolling for).

After rechecking the current code regarding this sysfs change at last
night, I found out that it's more broken for some devices like
sound/arm/*. They refer to card->dev to obtain the device for memory
allocation, etc, and passing card* object will screw them up.

The below is my current fix. Hoepfully all evils got away now... and
thanks for Monty for heading up this issue!

Takashi

====
[PATCH] ALSA: Fix sysfs breakage

The recent change for a new sysfs tree with card* object breaks the
/sys/class/sound tree if CONFIG_SYSFS_DEPRECATED is enabled.
The device in each entry doesn't point the correct device object:

/sys/class/sound
...
|-- pcmC0D0c
| |-- dev
| |-- device -> ../../../class/sound/card0
| |-- pcm_class
| |-- power
| | `-- wakeup
| |-- subsystem -> ../../../class/sound
| `-- uevent

Also, this change breaks some drivers (like sound/arm/*) referring
card->dev directly to obtain the device object for memory handling.

This patch reverts the semantics of card->dev to the former version,
which points to a real device object. The card* object is stored in a
new card->card_dev field, instead. The device parent is chosen either
card->dev or card->card_dev according to CONFIG_SYSFS_DEPRECATED to
keep the tree compatibility.
Also, card* isn't created if CONFIG_SYSFS_DEPRECATED is enabled. The
reason of card* object is a root of all beloing devices, and it makes
little sense if each sound device points to the real device object
directly.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
include/sound/core.h | 18 +++++++++++++++---
sound/core/init.c | 18 +++++++++++-------
sound/core/sound.c | 4 +---
sound/core/sound_oss.c | 4 +---
4 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/include/sound/core.h b/include/sound/core.h
index a994bea..521f036 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -132,8 +132,10 @@ struct snd_card {
int shutdown; /* this card is going down */
int free_on_last_close; /* free in context of file_release */
wait_queue_head_t shutdown_sleep;
- struct device *parent;
- struct device *dev;
+ struct device *dev; /* device assigned to this card */
+#ifndef CONFIG_SYSFS_DEPRECATED
+ struct device *card_dev; /* cardX object for sysfs */
+#endif

#ifdef CONFIG_PM
unsigned int power_state; /* power state */
@@ -191,6 +193,16 @@ struct snd_minor {
struct device *dev; /* device for sysfs */
};

+/* return a device pointer linked to each sound device as a parent */
+static inline struct device *snd_card_get_device_link(struct snd_card *card)
+{
+#ifdef CONFIG_SYSFS_DEPRECATED
+ return card ? card->dev : NULL;
+#else
+ return card ? card->card_dev : NULL;
+#endif
+}
+
/* sound.c */

extern int snd_major;
@@ -257,7 +269,7 @@ int snd_card_file_add(struct snd_card *c
int snd_card_file_remove(struct snd_card *card, struct file *file);

#ifndef snd_card_set_dev
-#define snd_card_set_dev(card,devptr) ((card)->parent = (devptr))
+#define snd_card_set_dev(card,devptr) ((card)->dev = (devptr))
#endif

/* device.c */
diff --git a/sound/core/init.c b/sound/core/init.c
index 6152a75..a4cc6b1 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -361,8 +361,10 @@ static int snd_card_do_free(struct snd_c
snd_printk(KERN_WARNING "unable to free card info\n");
/* Not fatal error */
}
- if (card->dev)
- device_unregister(card->dev);
+#ifndef CONFIG_SYSFS_DEPRECATED
+ if (card->card_dev)
+ device_unregister(card->card_dev);
+#endif
kfree(card);
return 0;
}
@@ -497,12 +499,14 @@ int snd_card_register(struct snd_card *c
int err;

snd_assert(card != NULL, return -EINVAL);
- if (!card->dev) {
- card->dev = device_create(sound_class, card->parent, 0,
- "card%i", card->number);
- if (IS_ERR(card->dev))
- card->dev = NULL;
+#ifndef CONFIG_SYSFS_DEPRECATED
+ if (!card->card_dev) {
+ card->card_dev = device_create(sound_class, card->dev, 0,
+ "card%i", card->number);
+ if (IS_ERR(card->card_dev))
+ card->card_dev = NULL;
}
+#endif
if ((err = snd_device_register_all(card)) < 0)
return err;
mutex_lock(&snd_card_mutex);
diff --git a/sound/core/sound.c b/sound/core/sound.c
index 2827420..82a61c6 100644
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -238,7 +238,7 @@ int snd_register_device(int type, struct
{
int minor;
struct snd_minor *preg;
- struct device *device = NULL;
+ struct device *device = snd_card_get_device_link(card);

snd_assert(name, return -EINVAL);
preg = kmalloc(sizeof *preg, GFP_KERNEL);
@@ -263,8 +263,6 @@ int snd_register_device(int type, struct
return minor;
}
snd_minors[minor] = preg;
- if (card)
- device = card->dev;
preg->dev = device_create(sound_class, device, MKDEV(major, minor),
"%s", name);
if (preg->dev)
diff --git a/sound/core/sound_oss.c b/sound/core/sound_oss.c
index b2fc40a..4566df4 100644
--- a/sound/core/sound_oss.c
+++ b/sound/core/sound_oss.c
@@ -106,7 +106,7 @@ int snd_register_oss_device(int type, st
int cidx = SNDRV_MINOR_OSS_CARD(minor);
int track2 = -1;
int register1 = -1, register2 = -1;
- struct device *carddev = NULL;
+ struct device *carddev = snd_card_get_device_link(card);

if (card && card->number >= 8)
return 0; /* ignore silently */
@@ -134,8 +134,6 @@ int snd_register_oss_device(int type, st
track2 = SNDRV_MINOR_OSS(cidx, SNDRV_MINOR_OSS_DMMIDI1);
break;
}
- if (card)
- carddev = card->dev;
register1 = register_sound_special_device(f_ops, minor, carddev);
if (register1 != minor)
goto __end;